Hydraulic pumping apparatus



Oct. 16, 1962 s. v. SMITH 3,

HYDRAULIC PUMPING APPARATUS Filed Oct. 17, 1960 5 Sheets-Sheet 1 ISFIMUEL I TSM/TH INVENTOR AT TO'RNEY CABL-E Oct. 16, 1962 s. v. SMITH HYDRAULIC PUMPING APPARATUS Filed Oct. 17, 1960 3 Sheets-Sheet 2 Z a J 5 I HR 3 T o 7 4K4. MW; n 5 Z .N Q m .L w Y mm i| m u I I W H w a s w m n m. I 2 1 5 1 \k j 6 m m I H 204 q 6 w W 8 5 m W 5 7 m .4 5 a ATTORNEY Oct. 16, 1962 s, v s

HYDRAULIC PUMPING APPARATUS 3 Sheets-Sheet 3 Filed Oct. 17, 1960 SQMUEL. 15 5M TH INVENTOR.

ATTORNEY nite States This invention relates to apparatus used for pumping wells and more particularly to improvements in fluid pressure powered pump jacks operable to raise and lower well pump rods and the like.

In general, fluid pressurized pump jacking units presently in use are characterized in construction as extending to a considerable height above the ground and over the well, it being conventional practice to mount a large pumping assembly vertically over the pump rod for supporting the latter and for reciprocating it in the well. However, at the present time there is increasing public and civic expression of a need for restricting the observable size of such equipment, particularly in residential areas where the benefits of petroleum production are recognized and sought at the expense of accommodating to the necessary presence of the production machinery. In addition, there has also been an increasing awareness of the attractive danger of conventional well pumping units to children, such as is encountered in the large pivoting booms of conventional pumping units.

In my Patent No. 2,947,144 entitled Pneumatic Hydraulic Pumping Apparatus, which issued August 2, 1960, there is disclosed and claimed an improved fluid pressure powered pump jack unit which minimizes the apparent size thereof to the observer While at the same time increasing the reliability and improving the operation of the equipment. The invention disclosed and claimed therein contemplates the provision of apparatus for vertically reciprocating a well pump rod or the like projecting above ground surface level, comprising a plurality of vertical cylinders spaced apart laterally so that they may be sunk downwardly into the ground in a laterally offset relation to the well, together with pistons reciprocal up and down in the cylinders and means for supporting the pump rod at its projection above ground by the pistons and for reciprocating the supported rod up and down in response to piston reciprocation. The pistons are then reciprocal below ground surface level by application of fluid pressure so that a large part of the equipment needed to lift and lower the pump rod is underground and out of sight of the observer.

In accordance with the apparatus described and claimed in the above entitled application the pistons and cylinders are preferably laterally spaced on opposite sides of a center corresponding to the well location, so that an aboveground cross-head structure interconnecting the piston rods may bridge over the well pump rod for reciprocating the latter as the pistons are displaced up and down in the cylinders. Such displacement is effected by means interruptedly communicating hydraulic pressure, for example, to a first pair of jacking pistons on opposite sides of the well and tending interruptedly to raise the pump rod, and also by means constantly communicating gas pressure to a second pair of balance pistons likewise spaced on opposite sides of the well and underground tending constantly to raise the pump rod. When the pressure communicated to the balance pistons is insuflicient alone to raise the pump rod, the latter is lifted only during communication of hydraulic pressure to the jacking pistons, interruption of such communication allowing the pistons to drop on the pump rod downstroke, the rate of drop being controlled by restricting the back flow of hydraulic fluid pushed from the cylinders by the pistons through a pump and valve arrangement.

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Patented Oct. 16, 1962 The present invention utilizes many of the principles of operation and construction set out in the copending application but is an improved and simplified apparatus for pumping fluid from a well. Although the invention described and claimed in my Patent No. 2,947,144 is eminently satisfactory, the present invention has certain advantages and improvements thereover including the increased simplicity in both construction and operation as more particularly pointed out hereinafter.

Accordingly, it is an object of the present invention to provide a hydraulic-pneumatic pumping unit which obviates the necessity for balance cylinders and pistons as discussed above.

It is another object of the present invention to provide an improved and simplified hydraulic-pneumatic pumping unit which includes a completely closed hydraulic circuit which is independent of fluid in the well.

Yet another object of the present invention is to provide a pumping unit of the type described wherein the polish rod load is balanced 'by a closed hydraulic system.

It is another object of the present invention to provide a fluid power hydraulic-pneumatic pumping unit which has a low fluid loss in a closed hydraulic system such that no scavenger system is required.

It is a further object of the present invention to provide such a fluid-power pumping unit system which provides adjustment for the length and placement of the stroke of the polish rod.

Yet another object of the present invention is to provide such a fluid-power pumping unit system which provides a positive shifting action between the up and down strokes of the polish rod within the well with a very soft reversal action.

It is a principal object of the present invention to provide a fluid power pumping unit that is designed to utilize hydraulic rams which raise and lower the polish rod within the well, which rams may be mounted below ground level to reduce the overall height of the visible portions of the well pumping unit and to provide quick accessibility to the well for well servicing jobs.

The present invention is a balanced pneumatic-hydraulic pumping unit adapted to be aflixed to a pump or polish rod extended above the well head for pumping well fluid from the well within which the pump rod is reciprocal and comprises a fluid cylinder positioned proximate the well and extending substantially parallel thereto from a position above the well head to a position substantially below the well head. A longitudinally movable piston is positioned within the fluid cylinder and is movable therein by introduction of fluid under pressure into the cylinder whereby the fluid pressure exerts an upward force on the piston. The piston is connected to the pump rod such that the pump rod is moved upwardly with the piston. A fluid reservoir is provided together with means for maintaining air under pressure in the reservoir above the fluid contained therein. The pressure of the air is variable to provide a pressure balanced system. A pump is connected between the reservoir and the fluid cylinder, the pump being of the type which can be reversed as to its direction of flow during the operation of the pump. Fluid lines are connected between the pump and the fluid cylinder and between the pump and the reservoir such that fluid under pressure is pumped to the fluid cylinder by the pump and returned from the fluid cylinder to the reservoir.

In the drawings:

FIGURE 1 is a view in elevation of the presently preferred embodiment of the present invention shown partially diagrammatically for purposes of clarity;

FIGURE 2 is a plan view corresponding to FIGURE 1;

3 FIGURE 3 is an enlarged vertical cross-sectional view of the invention taken on line 3-3 of FIGURE 1;

FIGURE 4 is an enlarged fragmentary side elevational viewpartly in section showing the portion of theinvention used for reversing the direction of rflow of fluid through the pump and the direction of movement of the polish rod;

FIGURE 5 is a horizontal cross-sectionalview of the invention;

FIGURE 6 is a partial view in cross-section taken along line 66 of FIGURE 4;

FIGURE 7 is a partial view in elevation taken along line 77 of FIGURE 4;

FIGURE 8 is a partial view in perspective of the cam bar of the present invention;

FIGURE 9 is a plan view taken along line 9'-9 of FIGURE 1;

FIGURE 10 is a partially schematic view taken along line 1010 of FIGURE 2;

FIGURE 11 is an enlarged viewin section of the air compressor utilized in the present invention;

FIGURE 12 is a partial view of the valve rings of the V compressor in the pumping portion of the pump;

:element of the apparatus of the present inventiona variable displacement fluid pump Pis utilized, which pump is of the type wherein the rate of'fluid'discharged can'be controlled and the direction of flow of fluidifrom'the pump can be reversed, with either or both of these controls being possible while the pump is operating. Al-

though other pumps of this type canbe utilized, the pump used in the presently preferred embodiment of the apparatus is of the type disclosed and claimed in copending application Serial No. 792,354, filed February 10, 1959,

by Samuel V.Smith and titled Reversible Discharge Flow Variable Displacement Pump. This pumpis a vane-type reversible hydraulic pump which reversesithrough neu .tral in order to soften out the reversing action of the fluid passing into and out of the pump. Thus, referring particularly to FIGURE 3, during the operation of the pump to cause fluid flow in one direction, one of the conduits 24 will serve as the inlet to the pump P while the other conduit 23 will serve as the outlet fromt-he pump. When the direction of fluid flow is reversed in the pump thefunction of the conduits will also be'reversed in that thefirst conduit 24 serves as the outlet whilethe second conduit 23 serves as the inlet. The pump is of the type in which the direction of fluid flow is reversed by mechanically moving a case 27 within the pump housing by means of a mechanical linkage which includes an operating rod 25 extending through'the housing and connected to the case. In general terms, the fluid pump P which is found to be particularly suitable for use in the present invention includes a driveshaft 21 to which a cylindrical rotor 18 is rigidly affixed witha plurality of blades 19 slidably mounted in a plurality of circumferentially spaced radially disposed slots formed in the rotor that extend inwardly from the periphery of the rotor. A rigid ring 22 having an internal diameter greater than that of the rotor surrounds the rotor and blades and is engageable by the outer ends of the blades to define a succession of arcuate spaces betweenthe ring, or case, and the rotor. The ring is slidably mounted for movement along a diameter of the rotor by a control rod '25 which extends outwardly from the-ring member and through the housing 20. The control rod is slidand by moving the control rod along the direction of cylinders.

its axis the ring 22 surrounding the vanes of the rotor can be shifted from a first position in which fluid is exhausted from the conduit 24 and is brought to the pump through the conduit 23, to the reverse position in which the conduit 24 serves as the inlet and the conduit serves as the outlet from the pump. For purposes of description throughout the following specification the conduit 24, which extends from the fluid pump P to the reservoir A, will be referred to as the inlet conduit while the conduit extending from the fluid pump P to the well unit will be referred to as the fluid outlet conduit. When the pump P is driven by the prime mover B at a constant rate it discharges fluid through conduit 23 at a first rate when case 27 is in a first position, and through conduit 24 at a second rate when case 27 is in a second position.

Referring now particularly to FIGURES 1, 2 and 3, the apparatus of the present invention includes a reservoir A which contains suitable hydraulic fluid. A pair of operating cylinders C and C' are extended vertically and are laterally spaced on opposite sides of an underground well casing 30 within which a polish rod or pump rod 31 is reciprocated to extract fluid from the well above the well head 32. The operating cylinders C and C extend from a position above the well head downward to an underground location within casings 34, 34' which serve to locate and position the operating cylinders C and C with respect to the well casing and provide accessibility to the cylinders and removal of the cylinders from the underground location. The lower ends of the casings'34, 34' are closed by suitable means such as steel plugs to maintain a fluid-tight condition, and the cylinders are supported by means such as concrete pads 35, 35' to support the vertical load and forces imposed on the The upper ends of the cylinders are affixed to cylinder heads 36, 36' by means of which the fluid connections to the cylinders are made as shown in FIG- URE 9. Thus, referring to FIGURES 1, 2 and 9, the control cylinders C, C are interconnected by a fluid connection member D which includes the first and second cylinder heads 36 and 36 which are joined by a fluid cross-member 37 in communication with both of the-cylinder heads 36 and 36' through fluid ports 38 and 38. A fluid inlet to the fluid connection 37 is provided at 40 for admitting fluid to each of the cylinders simultaneously and allowing removal of fluid from each of the cylinders. A fluid outlet 41 is provided to allow the discharge of well fluid from the interior 42 of the well casing 30 upon the upward stroke of the pump rod 31. Within the cylinders C, C a first piston and rod 44 and a second piston and rod 44' are reciprocable and are interconnected by a cross-member 45 to assure their simultaneous movement. The cross-member 45 extends above the well head 32 and is interconnected with the pump rod 31 such that upward and downward movement of the pistons and rods 44 and 44' causes simultaneous upward and downward movement of the pump rod 31. The pistons and rods 44 and 44 terminate at their lower ends in transversely extending piston faces 46 and 46 upon which fluid under pressure in the cylinders C, C can operate to force-the pistons upward. Thus, if fluid under pressure is forced into the cylinders C, C, it progresses downwardly around the pistons and rods 44, 44' between the exterior of the pistons and the interior of the cylinders C, C which is spaced therefrom. The fluid thus progresses from the fluid inlets 38 and 38' downward to fill the cylinders and exert fluid pressure upon the piston faces 46 and 46. When the fluid within the cylinders C, C is pressurized sufliciently, the force upon the piston faces will raise the pistons and the pump rod 31 attached thereto to cause discharge of well fluid from the outlet 41 where it progresses through the well fluid conduit 47 through a suitable valve 48 and into a well fluid reservoir 4-9.

A control cam described more fully hereinafter is afl'ixed to one of the pistons and rods 44' at the upper end thereof exteriorly of the cylinder and extends downwardly within the casing 34 substantially parallel to the control cylinder C. The control cam is shown in detail in FIGURE 4 and in a partial perspective View in FIGURE 8.

Referring now to FIGURES l, 2, 4 and 5, the apparatus of the present invention for operating the fluid pump P from the first position at which the pump is in the condition where fluid is pumped through the conduit 23, as the outlet conduit, and from the reservoir A through the inlet conduit 24, to the second position in which the flow of fluid through the pump is reversed such that fluid flows to the pump through the conduit 23 and from the pump to the reservoir through the conduit 24, is shown. As discussed hereinbefore, movement of the pump from the first to the second position, and from the second to the first position is achieved by moving the control rod 25 along the axis thereof. A fluid equalizing line 26 connects the opposite sides of the movable case to equalize fluid pressure caused by movement of the case within the pump housing. In the presently preferred embodiment this movement of the pump is obtained by utilizing a flexible push-pull cable of the type wherein a conduit which is flexible is affixed to the stationary portion of the housing 20 of the pump P while an inner cable which is longitudinally movable with respect to the outer conduit is aflixed to the control rod 25. Push-pull cables of this type are well known to the art for many similar push-pull applications. Thus, one end of the cable 50 is attached at the pump P with the movable cable 51 aflixed to the control rod 25' for movement therewith. The other end of the cable which is a part of the reversal mechanism is located adjacent the cylinder C, as shown schematically in FIGURE 1.

Thus, as shown in FIGURES 4 and 5, longitudinal movement of the push-pull rod 52 results in a corresponding movement of the push-pull cable 51 and the control rod 25 to move the fluid pump P from one position to the opposite position. The reversal mechanism which cycles the movement of the push-pull rod to the proper time with respect to the upward-downward movement of the pump rod 31 is shown in detail in FIGURES 4 through 8. The push-pull rod 52 is connected through a sealed housing 53 to cam follower rollers 54 and 55 such that horizontal movement of the cam followers 54 and 55 in either direction causes the push-pull rod 52 to be moved therewith. Since the fluid pump P will pass through a neutral position an off-center mechanism is provided for preventing the push-pull rod 52 from being stopped at the position corresponding to the neutral position of the pump such that the pump is at all times in the condition where it is pumping fluid in one direction or the opposite direction. The off-center mechanism F is described in detail hereinafter.

The housing 53 is located as shown in FIGURES 1 and 2 proximate the cylinder C such that the push-pull rod 52 extends in a substantially horizontal position. The cam bar 58 is a T-shapcd beam with cams 60 and 61 aifixed at opposite sides of the web 62 of the T-beam as shown in FIGURES 4 and 5. The cam bar extends vertically and is affixed at its upper end 63 to a bracket 64 which is in turn affixed to the piston and rod 44' and the cross-head 45 for movement upward and downward with the pump rod 31. The web 62 thus extends verti cally and is oriented transverse to the axis of the pushpull rod 52. The earns 60 and 61 are affixed at opposite sides of the web 62 and are triangular in configuration with an apex 66 and 67 respectively which projects outwardly from the surface of the web 62 by an amount suflicient to cause the push-pull rod to move the pump from one condition to the other condition. At the lower end of the cam bar there is affixed a guide follower 70 which is a roller rotatably mounted upon a shaft 71 as shown in FIGURES 4 and 7 to retain the cam bar in its vertical orientation during the upward and downward movement of the pump rod 31. Thus, there is aflixed to the housing 53 a bracket 72. to which is in turn affixed a vertically oriented guide 73 of rectangular cross-section having a depth greater than the width of the cam bar and a width substantially equal to the diameter of the guide follower 76. The guide 73 extends vertically within the casing 54 as shown in FIGURE 1. Thus, the cam bar and the guide follower 70 can move upward and downward in the guide means '73 with the guide follower in rolling contact with opposite sides thereof to maintain the cam bar in a vertical and aligned condition. The cam followers 54 and 55 are affixed to the push-pull rod 52 at the inner end 75 thereof by means of a channelshaped bracket 76. The bracket 76 provides an off-set mounting surface 77 to which the cam followers 54 and 55 are rotatably aflixed with the transverse center line of the cam followers being substantially aligned with the axis of the push-pull rod 52. The axis of rotation of the cam followers 54 and 55 are spaced apart sufliciently that the opposed surfaces 78 and 79 of the cam followers which bear upon the cam bar 58 are spaced at a distance sufficient that one surface 78 is approximately in contact with one surface of the web 62 when the opposite cam follower surface 79 is at the position of the apex 67 of one of the camlobes. Thus, the cam followers are spaced to allow horizontal movement of the push-pull rod 52 by a horizontal distance equal to the height of the cam lobe above the surface of the web 62. A series of holes are placed through the web 62 mateable with openings through cams 60 and 61 such that the cams can be moved to various locations on the web to adjust the position of the apexes 66 and 67. Thus, the cams can be moved toward one another and affixed to the cam bar or can be moved away from one another, or their positions can be changed independently. Thus, the position of the pump rod 31 at which the cam 60 or the cam 61 causes a reversal of fluid flow from the fluid pump P can be varied through an infinite number of positions. As discussed more fully hereinafter, the pump will be reversed in direction when the apex 66 or the apex 67 passes between the cam followers 54 and 55.

A bracket 80 is aflixed to the guide means 73 and extends upward to a position at which it furnishes a mounting surface 81 for attaching a horizontal guide means 82. The horizontal guide means is a roller 82 rotatably affixed to the bracket 80 and extends to a position substantially aligned with the cam followers 54 and 55. The horizontal guide means 82 is mounted such that it extends into a horizontally extending groove 84 in an extending arm 85 of the bracket 75 with the diameter of the guide means 82 and the height of the groove 84 being such that the guide means 82 restricts the bracket 76 to horizontal movement with respect to the cam bar.

Bearing means 80 and 91 are provided at opposed faces of the housing 53 to surround the push-pull rod 52 as supports and bearings therefor to allow only horizontal movement of the control rod 52. Sealing means such as O-rings 92 and 93 are provided within the bearings and 91 to provide fluid sealing surrounding the push-pull rod 52 such that the interior of the housing 53 is closed and sealed. The upper and lower cams 6t} and 61 respectively, as shown in FIGURES 4 and 8, are positioned on the cam bar at opposite sides of the web 62 thereof to provide reversal of the pump P at the desired upper and lower positions of the pump rod 31 during its stroke. The upper cam 60 is positioned on the cam bar such that the apex 66 of the cam passes beneath the cam follower 55 at the lowest desired position of the pump rod 31, while the lower cam 61 passes beneath the cam follower 54 with the apex 67 of the cam located at the position corresponding to the uppermost desired position of the pump rod 31. Accordingly, it is required that the pushpull rod 52 be moved only when the lowermost and uppermost position of the pump rod 31 is achieved. That is, during the downward stroke of the pump rod 31 and the corresponding downward movement of the cam bar 58, the push-pull rod 52 will not change in position until the upper cam 60 passes beneath the cam follower 55. As the cam 60 moves downward between the cam followers 54 and 55, it will force the cam follower 55 to the left in FIGURES l and 4 until the cam follower 55 and the control rod 52 have been moved a distance to the left corresponding to the height of the apex 66. It is necessary that this position of the control rod 52 be maintained until the uppermost position of the pump rod 31 is reached. This movement is obtained by means of the offcenter cam mechanism positioned within the housing 53 and operable by the push-pull rod 52.

Thus, referring to FIGURES 4, and 6, a pair of spaced-apart T-shape-d brackets 101 and 102 are afiixed to the forward end 103 of the housing 53 and extend outwardly therefrom with vertically oriented legs 104 and 105 provided on the T-brackets 101 and 102. First and second cam follower shafts 106 and 107 are extended through the legs 104 and 105 proximate the ends thereof such that the shafts 106 and 107 are vertically spaced apart by a substantial distance above and below the pushpull rod 52 and extend substantially transversely thereto. The cam follower shafts 106 and 107 are vertically movable by being mounted in vertically extending slots 108 and 109. The shafts are resiliently interconnected by means of springs 110 and 111 which exert a spring force upon the cam follower shafts to move them toward one another. Upper and lower cam followers 112 and 113 are rotatably mounted upon the shafts 106 and 107 for movement therewith. The cam followers 112 and 113 are thus restrained to vertical movement and are urged vertically together toward the push-pull rod 52. An olfcenter cam 115 is affixed to the push-pull rod for longitudinal movement therewith. In the embodiment shown the cam is formed separately and is a plate of substantial width and hexagonal configuration oriented as shown in FIGURE 4. The push-pull rod is threadably connected at opposite vertical faces 116 and 117 of the cam 115 such that the push-pull rod 52 is divided into two sections which are oriented along a common axis. The upper and lower faces of the cam 115 are divergent from the vertical faces 116 and 117 to an upper apex 120 and a lower apex 121 which are vertically opposed. Thus, the cam has divergent faces 123 and 124 extending from the forward vertical face 116 and divergent faces 125 and 126 extending from the rearward vertical face 117. The forward faces 123 and 124 are shorter than the rearward faces 125 and 126 in order that the apexes 120 and 121 do not occur at the longitudinal center point of the cam Accordingly, the cam followers 112 and 113 are urged inwardly toward the push-pull rod 52 while bearing on the forwardly inclined surfaces 123 and 124, or on the rearwardly inclined surfaces 125 and 126, of the cam 115, dependent upon the longitudinal position of the cam. When the cam followers 112 and 113 are on the forwardly inclined surfaces 123 and 124 to the left of the apexes 120 and 121 in FIGURE 4, the spring action urging the cam followers together will exert a force upon the cam 115 and the push pull rod 52 urging the cam and push-pull rod to the right-hand position of FIGURE 4. The lower cam 61 shown in FIGURE 4 has urged the push-pull rod 52 to the right to the position at which the cam followers 112 and 113 rest on the forwardly inclined surfaces 123 and 124. Once the cam followers 112 and 113 have passed to the right of the apexes 120 and 121 they will by the inward force acting on the inclined surfaces push the push-pull rod and cam to its extreme right-hand position and will maintain it in this position until the push-pull rod is urged positively to the left.

Thus, during the downward movement of the cam bar the push-pull rod 52 will remain in the right-hand position with the cam follower following the left surface of the web 62. That is, the push-pull rod 52 will not be urged to the left until the upper cam passes between the cam followers and moves the cam follower assembly to the left. As the cam follower 55 passes the apex 66 on the cam 60, the cam followers 112 and 113 pass to the right of the apexes and 121 of the off-center cam 115 and will urge the cam 115 and push-pull rod 52 to its left-hand position until again moved positively to the right.

Referring now to FIGURES 1, 2 and 4, when the cam bar and push rod mechanism have caused the push rod 52 in FIGURE 4 to be moved to the left-hand position as shown in the figures by causing the cam follower 55 to pass over the apex 66 of the upper cam 60, the fluid pump P is moved to the position at which it is to pump fluid under pressure into the cylinders C to raise the pistons 44 and 44' and the pump rod 31. That is, when the upper cam 60 on the cam bar positions the push-pull rod 52 to the left, the pump is moved to the position at which the fluid conduit 23 is the outlet of the fluid pump P, and the fluid conduit 24 serves as the inlet. At this position, therefore, fluid is pumped from the reservoir A through the fluid pump P and into the cylinder C to act upon the piston faces 46 and 46' and raise the cylinders 44 and 44' together with the pump rod 41. When the pump rod 31 has reached its uppermost position the lower cam 61 on the cam bar 58 passes beneath the cam followers and moves the push-pull rod 52 to the right as described hereinbefore. Movement of the push-pull rod 52 to the right causes the position of the fluid pump P to be reversed whereby fluid is pumped from the cylinders C and back into the reservoir A such that the fluid conduit 23 acts as the fluid inlet to the pump, while the fluid conduit 24 acts as the outlet from the pump and to the reservoir. A typical stroke length of the pump rod 31 is three feet.

In order to obtain a balanced hydraulic pneumatic system the accumulator tank A is filled with suflicient fluid to transmit fluid from the accumulator to the cylinders C in suflicient quantity and under sufficient pressure to raise the pistons 44 and 44' the required distance under the load exerted upon the polish rod. Air under pressure is, however, maintained within the accumulator above the fluid supply and the pressure of the air is maintained sufficiently high to obtain a balancing force upon the fluid. That is, a typical polish rod load isl 1,000 pounds and the system of the present invention furnishes a balancing load of 7500 pounds, such that it is necessary only that the pump exert a force equal to the differential between the air pressure above the fluid and the pressure upon the fluid in the cylinders C necessary to raise a load of 11,000 minus 7500 pounds.

Thus, in the presently preferred embodiment a small two-stage reciprocating air compressor G is mounted above the accumulator and directly connected thereto. The compressor is driven by fluid under pressure from the pump P and supplies air under pressure to the accum' ulator to maintain the pressure within the accumulator at a predetermined value dependent upon the balancing load required. When the pressure within the tank exceeds the predetermined value, a relief valve 130 is opened, which relief valve is set at the balance pressure to exhaust air from the accumulator. Referring now to FIGURES 10, 1 and 11 through 14, a compressor G in accordance with the present invention is shown. As shown particularly in FIGURE 11, the compressor includes a cylindrical housing which is divided into longitudinally extending sections by a first transverse plate 136 and a second transverse plate 137. The cylindrical housing is closed at the upper end thereof by an upper plate 138 and at the lower end thereof by a lower plate 139. The first and second transverse plates 136 and 137 are substantially equally spaced from the upper plate 138 and the lower plate 139' respectively in order to define a first interior portion 140 and a second interior portion 141 which are of substantially equal length. Positioned within the upper portion 140 is a driving piston 142 which is interconnected with a pumping piston 143 positioned within the lower portion 141. The driving piston 142 and the pumping piston 143 are interconnected by a piston rod 144 which is greater in diameter within the lower cylinder than within the upper cylinder. An opening 145 is provided through the first transverse plate 136 substantially on the longitudinal center line of the cylindrical housing. The upper piston rod 144a is in sliding contact with the opening 145 and is sealed with respect thereto by suitable sealing means such as rings 147. Similarly, the lower portion of the piston rod 144]) is connected with the upper surface of the pumping piston 143 and extends through an opening 148 defined by the second transverse plate 137. Sealing means such as O-rings 149 are also utilized to provide a fluid seal between the second transverse plate and the piston rod 144b.

A fluid port 150 is provided through the cylindrical housing proximate the upper end thereof such that fluid can be conducted into and out of the upper cylinder above the upper surface of the driving piston 142. In the embodiment shown the fluid port 150' is connected to a fluid line 151. Similarly, a fluid port 152 is provided to the upper cylinder 140 beneath the driving piston 142. In the embodiment shown, the fluid port 152 is defined in the first transverse plate 136 and extends from the edge thereof radially inward and then upward into communication with the cylinder 140. A similar air outlet 153 is provided through the second transverse plate 137 and is in communication with the exterior of the housing 136 and the lower cylinder 141 above the pumping piston 143. The port 153 acts as an air outlet from the cyllinder 141. An air inlet port 154 is formed in the lower plate 139 and has a conduit 155 in communication therewith. The conduit 155 is in fluid communication with the interior portion 156 of the cylindrical housing 135 between the plates 136 and 137. Thus, an air path is provided between the intermediate portion 156 of the cylindrical housing and the lower cylinder 141 beneath the pumping piston 143. An air inlet port 161! is formed in housing 135 and is in communication with the intermediate interior portion 156 thereof. Piston rings 161 :are mounted upon the pumping piston 142 to furnish a sliding sealing engagement between the pumping piston and the internal walls of the cylinder 1413.

Referring now particularly to FIGURES 11 through 14, there is positioned upon the circumference of the pumping piston 143 a plurality of piston rings which are constructed to permit the passage of air past the pumping cylinder 143 during the pump stroke in one direction while sealing the piston against the walls of the cylinder to prevent the passage of fluid between the piston and cylinder during the stroke of the piston in the opposite direction. Thus, as shown in the figures, two piston rings 170 in the presently preferred embodiment are mounted circumferentially upon the piston 143 in piston ring grooves 171 formed in the circumferential wall of the piston 143. The radial depth of the groove is such that the inside diameter of the toroidal rings 171 is mateable therewith. That is, in the position of the piston ring 171 at which the outer radial surface 172 thereof is in sliding contact with the internal wall 174 of the cylinder 141, the inner diameter 175 of the piston ring is in contact with the bottom wall 176 of the respective groove. The height of the groove 171 is such that it is substantially greater than the thickness of the ring 170. The distance between the walls 171a and 171b of the ring groove is substantially greater than the longitudinal thickness of the ring 170 such that the groove will permit longitudinal travel of the ring 170 therein. A plurality of fluid passages in the form of slots are provided in each of the rings. The slots 180 are radially extending and are circumferentially spaced such that a fluid communication exists between the inside diameter and outside diameter of the ring when the surface of the ring is in bearing or sealing contact with the side wall 171a of the groove 171. In the embodiment shown the radial grooves 180 are provided at circumferential intervals in the upper surface 181 of the ring 1711. Similarly, at a circumferentially mated position a longitudinally extending groove is provided in the inner wall of the ring, which groove 182 is in fluid communication with the radially extending groove 180.

As shown in FIGURES 12 through 14, a fluid path is provided around the ring 171) when the ring is in the position at which its upper surface is in contact with the side wall 171a of the groove 170. Fluid at this position of the ring can pass beneath the ring between the ring and lower surface 171k of the groove 171, and thence upward through the longitudinally extending slot 182 and outward through the radially extending slot 130. The fluid can then pass upward through the space existing between the outside diameter of the piston 143 and the internal wall 174 of the cylinder.

When utilized to maintain the air under the required pressure in the accumulator A of the present invention the compressor G is connected with the accumulator by connecting an air passage line 190 between the air outlet 153 of the compressor and into the accumulator at a position above the normal liquid level therein at the air inlet 191. A suitable shut-off valve 192 is provided in the line. The fluid inlet port 150 of the compressor G and a fluid outlet from the pump P as shown in FIGURE 10 are connected by the fluid line 151, which line has a shut-off valve 151a therein. A second fluid connection is made between the fluid port 152 and a fluid outlet of the pump P by means of a fluid line 1%. Therefore, as described hereinbefore, the pump P will supply fluid to the cylinder 14!) under pressure and at a reversing position such that fluid flows into the interior cylinder portion through the fluid inlet 151) and upon reversal of the pump P the fluid port acts as a fluid outlet while fluid is pumped into the cylinder 140 through the fluid port 152. Accordingly, the driving piston 142 is driven upward and downward within the compressor G alternately with each reversal of the pump P. Upon the upward and] downward stroke of the driving piston 142, the pumping piston 143 acts to pump air from the compressor through the air port 153 and into the accumulator through the air line 190. During the downward stroke of the piston 143 the rings 170 within the grooves 171 are forced upwardly until the upper surface 181 of each ring is in contact with the upper side Wall 171a of the groove, as shown in FIG- URE 13. At this position of the rings, that is, during the downward stroke of the pumping piston 143, air which may contain a certain amount of oil picked up from the intermediate cylinder 156 will progress upwardly between the outer wall of the piston, beneath the rings 170, upward through the longitudinally extending grooves 182, outward through the radially extending grooves 130 and thence upward into the upper portion of the cylinder 141. When the piston begins its upward travel, the rings 170 act as a seal in combination with the piston by moving to the position shown in FIGURE 12 at Which the surface 172 of the piston ring comes into sealing contact with the lower side wall 171b of each groove such that no air or other fluid can pass therebetween.

Thus, the rings 170 provide a fluid seal during the upward stroke of the piston 143 aand allow a fluid passage during the downward stroke of the piston. Accordingly, during the upward stroke of the piston, air is forced from the cylinder 141 through the air outlet 153 and during the downward stroke of the piston air which was carried into the cylinder 141 through the air line from the intermediate cylinder 156 is passed upward past the pumping cylinder 143. The compressor G driven by the pump P exhausts air through the air outlet port 153 during each of the upward strokes of the piston and entraps air aoesises 11 abovethe piston duiing'ea'chof the downward strokes thereo'f.

What is claimed is:

1. A hydraulically operated pumping unit for reciprocating a vertically disposed pump rod comprising:

(a) first and second vertically extending cylinders disposed adjacent said rod at opposing sides thereof;

(1)) piston means upwardly and downwardly reciprocable in each of said cylinders;

(c) a fluid flow path to said cylinders and beneath said pistons whereby said pistons are raised within said cylinders by fluid admitted to said cylinders at a first predetermined fluid pressure and lowered by the removal of fluid therefrom, said pistons being operatively connected to said pump rod for reciprocation therewith;

(d) a prime mover;

(e) a rotary fluid pump capable of occupying first and second positions, said pump being rotated in one direction by said prime mover, which pump moves fluid into said fluid path at said first pressure when in said first position and from said cylinders through said fluid path when in said second position, with said pump being movable to said first and second positions during the rotation thereof;

(1) a reservoir partially filled with hydraulic fluid, a quantity of gas at a second predetermined pressure within said reservoir;

(g) compressor means for maintaining said gas substantially at said second pressure, which compressor means includes a longitudinally extending housing defining a driving cylinder and a compressor cylinder, a driving piston longitudinally movable within said driving cylinder in response to fluid pressure at one surface of said driving piston, a first fluid conduit connected between one side of said fluid pump and one side of said driving piston, a second fluid conduit connected between the opposite side of said fluid pump at the opposite side of said driving piston whereby said driving piston is reversed in direction when said fluid pump is reversed in direction, a compressor piston longitudinally movable within said compressor cylinder, an air inlet to one side of said compressor piston in said compressor cylinder and an air outlet from said cylinder at the opposite side of said compressor piston, a plurality of radially extending rings mounted upon the circumference of said compressor piston in radially extending grooves therein, said rings being longitudinally movable within said grooves to pass air thereby from the inlet to the outlet side of said piston during travel of said piston toward said inlet and to seal said compressor piston and cylinder during movement of said piston toward said outlet;

(/1) vertically movable cam means connected for reciprocation with said pump rod, said cam means including a vertically oriented cam surface, an upper and lower cam lobe extending horizontally from said cam surface, said lower lobe being spaced vertically beneath said upper lobe;

(i) a horizontally movable cam follower in bearing contact with said cam means, said cam follower being operatively connected to said pump whereby said pump is moved from said first to said second position by said cam follower upon movement by .one of said camsand from the second to the first positionby the other of said cams; and

(j) means interconnecting said pump rod and said fluid pump to change said fluid pump from said second to said first position at the bottom of the stroke of said pump rod and from said first to said second position at the top of said pump rod stroke.

2. The apparatus as defined in claim 1 wherein said cam follower means include means for retaining said follower at the position to which said follower is moved -byone cam lobe until saidfollowerispositively-engaged by-said other cam'lobe.

3. An apparatus for vertically reciprocating a loaded rod at a desired first uniform rate on the upstroke and a desired second uniform rate on the downstroke by a hydraulic liquid under pressure, including; a vertical cylinder disposed adjacent said rod; piston means upwardly and downwardly reciprocable in said cylinder as said liquid is discharged into said cylinder at a first pres sure and discharged from said cylinder at substantially a second pressure; means for connecting said rod to said piston means; a reservoir that is partially filled with said liquid and a quantity of air under such pressure that said liquid is at all times under no less than said second pressure, with said second pressure being of such magnitude that when said piston means is subjected to said liquid an upward force is exerted on said piston means that is equal to the weight of said rod plus a predetermined per centage of said load on said rod; a reversible discharge variable volume pump having first and second ports through either of which liquid can be discharged when said pump is rotated, said pump having an interior case that is capable of being disposed in a first off-centered position, a centered position, and a second off-centered position, with liquid being discharged through said first port at a first rate when said case is in said first position and through said second port at a second rate when said case is in said second position, with no discharge of liquid from said pump taking place when said case is in said centered position; first and second pipes, which first pipe connects said first port to the interior of said cylinder and said second pipe connects said second port to the interior of said reservoir; longitudinally extending rigid means for moving said pump case to either said first or second position; spring-loaded cam means connected to said longitudinally extending rigid means and operated by the movement of said rod for moving said case to said first position when said rod approaches the lower limit of its stroke and to said second position when said rod approaches the upper limit of its stroke; an air compressor that includes a reciprocable piston which, as said piston reciprocates, compresses air in said compressor; first conduit means for conducting compressed air from said compressor to the upper portion of said reservoir for maintaining said air in said reservoir at substantially said second pressure; and second conduit means connected to said compressor and the interior of said pump for alternately supplying liquid under pressure from said pump to first one side of said piston and then the opposite side of said piston for actuating said compressor to supply air under pressure to said reservoir to maintain said air therein at said second pressure as said longitudinally extending rigid means moves said casing to said first and second positions.

4. An apparatus for vertically reciprocating a loaded rod at a desired first uniform rate on the upstroke and a desired second uniform rate on the downstroke by a hydraulic liquid under pressure, including: a vertical cylinder disposed adjacent said rod; piston means upwardly and downwardly reciprocable in said cylinder as said liquid is discharged into said cylinder at a first pressure and discharged from said cylinder at substantially a second pressure; means for connecting said rod to said piston means; a reservoir that is partially filled with said l qu d and a quantity of air under such pressure that said liquid is at all times under no less than said second pressure, with said second pressure being of such magnitude that when said piston means is subjected to said liquid an upward force is exerted on said piston means that is equal to the weight of said rod plus a predetermined percentage of said load on said rod; a reversible discharge variable volume pump having first and second ports through either of which liquid can be discharged when said pump is rotated, said pump having an interior case that is capable of being disposed in a first oflf-cen- 13 tered position, a centered position, and a second off-cen tered position, with liquid being discharged through said first port at a first rate when said case is in said first position and through said second port at a second rate when said case is in said second position, with no discharge of liquid from said pump taking place when said case is in said centered position; first and second pipes, which first pipe connects said first port to the interior of said cylinder and said second pipe connects said second port to the interior of said reservoir; longitudinally extending rigid means for moving said pump case to either said first or second position; spring-loaded cam means connected to said longitudinally extending rigid means and operated by the movement of said rod for moving said case to said first position when said rod approaches the lower limit of its stroke and to said second position when said rod approaches the upper limit of its stroke; second conduit means connected to said compressor and the interior of said pump for alternately supplying liquid under pressure from said pump to first one side of said piston and then the opposite side of said piston for actuating said compressor to supply air under pressure to said reservoir to maintain said air therein at said second pressure as said longitudinally extending rigid means moves said casing to said first and second positions; and air compressor means for maintaining said air in said reservoir at said second pressure, which compressor means comprises a longitudinally extending housing defining a driving cylinder and a compressor cylinder, a driving piston longitudinally movable within said driving cylinder in response to liquid pressure at one surface of said driving piston, a first liquid conduit connected between one side of said pump and one side of said driving piston, a second liquid conduit connected between the opposite side of said pump at the opposite side of said driving piston whereby said driving piston is reversed in direction when said pump is reversed in direction, a compressor piston longitudinally movable within said compressor cylinder, an air inlet to one side of said compressor piston in said compressor cylinder and an air outlet from said cylinder at the opposite side of said compressor piston, a plurality of radially extending rings mounted upon the circumference of said compressor piston in radially extending grooves therein, said rings being longitudinally movable within said grooves to pass air thereby from the inlet to the outlet side of said piston during travel of said piston toward said inlet and to seal said compressor piston and cylinder during movement of said piston toward said outlet, and conduit means connecting said air outlet to the upper interior portion of said reservoir for conducting .air under pressure from said compressor means to said reservoir for maintaining said air in said reservoir at substantially said second pressure.

References Cited in the file of this patent UNITED STATES PATENTS 1,596,145 Black Aug. 17, 1926 2,313,404 Vickers Mar. 9, 1943 2,645,899 Aller et al. July 21, 1953 2,947,144 Smith Aug. 2, 1960 

